1. Field of the Invention
This invention relates to a testing apparatus used to electrically test semiconductor package devices.
2. Description of Related Art
Integrated circuits are usually housed within a protective ceramic or plastic package. The package has a plurality of leads that are soldered to a printed circuit board. Before the packages are mounted to the boards, the integrated circuits are usually individually tested to insure that the circuits are not defective. The packages are typically connected to a test circuit board by a number of spring biased leads that provide a conductive path between the package leads and the test board. The spring leads are arranged in a pattern to match the package leads, so that a spring lead engages and couples each package lead to the test board. Once connected, the integrated circuits are electrically tested by testing equipment connected to the test board.
The packages have leads that are designated for ground, power and digital signals. When engaged, the spring biased leads create an additional conductor length between the package leads and the test board. The additional conductor length generates inductive effects between the power leads and the signal leads, producing an undesirable amount of noise on the signal leads. The electrical noise can create faulty test results, which incorrectly indicate that the integrated circuit is defective. The problem is particularly acute with high speed devices. An undeterminable number of packages are improperly rejected as bad, which results in a lower yield of parts.
One possible solution is to decrease the amount of power on each power lead. This approach increases the number of power and ground leads required for each package for a given power. Increasing the power leads requires either a reduction in the number of signal leads, or a decrease in lead spacing. Both solutions are undesirable in that design trends always dictate more signal pins not less, and a decrease in lead spacing compromises the structural integrity of the package. Therefore it would be desirable to have an apparatus that couples a semiconductor package device with a test board that greatly decreases the noise in the testing apparatus.